Stem cells turned to blood

Wisconsin is at the forefront of stem cell research

Scientists have for the first time coaxed human embryonic stem (ES) cells into becoming blood cells.

It is an important step that could eventually lead to new blood products for use in transfusions and transplants.

But lead scientist Dan Kaufman, a hematologist at the University of Wisconsin-Madison, US, stressed that much work still needed to be done.

"There are potential clinical therapies that may develop in the future, but it's very clear that those therapies are many years off," he said.

ES cells are "master" cells found in early-stage embryos that have the capability to develop into virtually all tissue types in the body. Scientists believe that control over the development of these cells will open up a powerful new approach to the treatment of degenerative disease.

It is a controversial line of research because the method for obtaining the ES cells necessarily involves the destruction of human embryos. This has led some interest groups, such as the anti-abortionists and the Catholic Church, to campaign to have the research halted.

The difficult ethical issues involved led last month to US President George W Bush agreeing only to limited federal funding for stem cell research.

Bone marrow cells

Kaufman and his colleagues grew the human embryonic stem cells in culture with mouse cells that secrete factors promoting blood cell development.

They were able to show that the stem cells developed into primitive blood cells, known as hematopoietic precursor cells.

The precursor cells displayed biochemical markers and gene products that are characteristic of blood and bone marrow cells in the human body, and went on to form colonies of white blood cells, red blood cells and platelets, identical to those produced from human adult bone marrow cells.

All these major steps have been seen in previous work using mouse embryonic stem cells, but this study is a first for human cells, which have distinct differences both in terms of their physical features and the culture conditions necessary to promote growth.

Growing blood cells from stem cells may someday help alleviate shortages of blood needed for transfusions, or provide cells for blood or bone marrow transplants for patients with leukemia or other cancers, Kaufman said.

The research, supported in part by the University of Wisconsin Comprehensive Cancer Center and the WiCell Research Institute, is published in the Proceedings of the National Academy of Sciences.